Recently, the print speed is increased in image forming apparatuses widely used as printers and copiers and, for example, the number of printed sheets for standard A4 type is 100 to 120 sheets/min, which was 40 to 60 sheets/min some years ago. As the print speed is increased, sheet carriage intervals are shortened, and the number of sheets concurrently carried to a sheet path is increased. On the other hand, if sheets are jammed in the sheet path while an apparatus is operated, all the sheets remaining in the sheet path must be removed to restore the apparatus to the operable state after the drive of the sheet path is suspended.
However, if the print speed is increased as above, the number of sheets staying and remaining in the sheet path is also increased when the sheets are jammed, and a heavy burden is imposed due to the effort to remove these sheets. Therefore, although many propositions have been made to facilitate the removal of sheets remaining in the sheet path of the apparatus, a method is generally used to remove the sheets manually using several opening/closing means disposed in some portions of the sheet path of the apparatus.
In the disclosure of Japanese Laid-Open Patent Publication No. 61-055054, when jamming occurs in a carriage path after toner is transferred in an electrophotography apparatus, a non-fixed recording paper sheet is discharged as a fixed recording paper sheet to prevent toner from scattering and contaminating hands and clothes of an operator or the apparatus main body and the periphery of the apparatus at the time of removing the jammed paper sheets.
In the disclosure of Japanese Laid-Open Patent Publication No. 9-114156, a sheet path is driven by a plurality of drive systems, and jammed sheets are manually removed after stopping the drive system, on the other hand, sheets not jammed are returned to a paper feed tray or discharged to an emergency paper discharge tray by separately driving each of the drive systems.
In the disclosure of Japanese Laid-Open Patent Publication No. 11-059969, when a paper-leaf-shaped medium (such as paper money and security sheet) is carried from a first carriage path to a second carriage path, if a paper jam occurs on the way, the carriage direction of the second carriage path is switched to the opposite direction to collect the jammed sheet in a predetermined stacker.
In accordance with Japanese Laid-Open Patent Publication Nos. 9-114156 and 11-059969, when a jam occurs while carrying a sheet, the sheet in the carriage path can be carried in the opposite direction and automatically removed, and the removal of jammed paper by hand can be alleviated. However, when a sheet is carried from a carriage path of one unit to a carriage path of the other unit (i.e., when a sheet is carried from one of two carriage paths to the other carriage path), the carriage direction for removing the sheet varies depending on whether the sheet exist in which carriage path of the two carriage paths, and the detection of the sheet and the control mechanism become complicated.
When the jam occurs, one sheet may straddle two carriage paths (two units). In this case, it is difficult to control which direction one sheet should be carried for removal. When two carriage paths can be separated from each other, if the apparatus is opened, the sheet straddling two carriage paths may be guillotined and damaged, and the damaged sheet may be pinched by carriage rollers and become difficult to remove.